Physical quantity distribution sensor, method of driving said sensor and method of producing said sensor

ABSTRACT

A physical quantity distribution sensor is disclosed. The sensor comprises: a plurality of sensor/storage sections each having a sensor element for sensing a received physical quantity and a storage element for storing the information of physical quantity sensed by the sensor element; a selector for selecting at least one of the sensor/storage sections; and a plurality of buffers each capable of detecting and supplying the information stored in at least one selected sensor/storage section. This sensor further comprises at least one selection signal transfer line for transferring an output of the selector. Power supply input portions of the buffers are connected to the selection signal transfer line, and the buffers are operated using, as a power voltage, an output of the selector entered into the buffers through the selection signal transfer line.

BACKGROUND OF THE INVENTION

The present invention relates to a physical quantity distributionsensor, a method of driving said sensor and a method of producing saidsensor.

Recently, there is increased a demand for a semi-conductor device forsensing the spatial distribution of a physical quantity in a variety offields. Particular attention is placed on a solid-state imaging devicefor sensing a light quantity as the physical quantity. Morespecifically, such a so-called amplifier-type solid-state imaging deviceis designed in the following manner. A plurality of storage sections arearranged to store a signal electric charge obtained throughphoto-electric conversion at the associated one of a plurality ofphotoelectric conversion sections. Each storage section is connected tothe operation control portion of a transistor such as the gate of afield-effect transistor (FET) or the base of a bipolar transistor, orprovision is made such that the storage section also serves as anoperation control section. Accordingly, an electric current flowing ineach transistor is controlled based on that potential of the associatedstorage section which varies with the amount of a signal electriccharge.

With reference to FIG. 12, the following description will discuss thearrangement and operation of a physical quantity distribution sensor ofprior art with an amplifier-type solid-state imaging device taken as anexample.

As shown in FIG. 12, pixels 2 are arranged in a plurality of rows and aplurality of columns in an imaging region (generally, a region in whicha physical quantity is to be sensed and stored) 1. Each pixel 2comprises a photoelectric conversion/storage section 3 and a drivingtransistor 5 having a gate 4.

A selected-row-driving transistor 10 is disposed in eachselected-row-driver 8, and a voltage is to be supplied to eachselected-row-driving transistor 10 from a selected-row-driving-voltageinput portion 9. Whether or not each selected-row-driving transistor 10is electrically conductive, is controlled by a voltage of each outputportion 7 of a shift register for row selection 6. An output of aselected-row-driving transistor 10 is connected to a plurality ofrow-select-transistors 12 arranged in the row through one of rowselection lines 11, which allows a single pixel row to be selected outof the plurality of pixel rows.

The row-select-transistors 12 arranged in the same column are connectedto a corresponding one of load transistors 14 through one of verticalsignal lines 13. The output potential of each photoelectricconversion/storage section 3 varies with the amount of signal electriccharge stored therein. The output potential of each photoelectricconversion/storage section 3 is given to the gate 4 of a correspondingdriving transistor 5 which is connected to one of power supply lines 17.There is formed a source follower circuit in which the drivingtransistor 5 serves as a driving transistor and in which the loadtransistor 14 connected to a second power supply voltage (Vss) terminal15 and to a gate input portion 16, serves-as a load transistor. A powersupply voltage.(Vdd) is supplied to each power supply line 17 from afirst power supply voltage (Vdd) terminal 27.

An output of the source follower circuit including the drivingtransistor 5 and the load transistor 14 is supplied to one of horizontalsignal lines 24 through a signal column selection transistor 23 disposedin the associated one of column selection drivers 22. Whether or notsignal column selection transistors 23 are electrically conductive, iscontrolled by voltages generated at output portions 21 of a shiftregister 20 for column selection. According to this control, a singlepixel column is selected out of the plurality of pixel columns. Anoutput of the source follower circuit in a selected column, isselectively sent to an impedance conversion section 25 through thehorizontal signal line 24, and then supplied to an output portion 26through the impedance conversion section 25.

After the signals are read out from all the pixels 2 arranged in theselected row, a reset voltage input portion 28 sends a reset voltage tothe selected-row-reset-driving transistor 29 in the selected-row-driver8 for the selected row, thereby to drive the pixel reset transistors 30in the selected row through a pixel-reset-voltage-supply line 19associated with the selected row. This resets the signal electriccharges stored in the photoelectric conversion/storage sections 3 in theselected row. Then, these photoelectric conversion/storage sections 3again start storing signal electric charges.

According to the above-mentioned arrangement of prior art, each pixelhas a photoelectric conversion section and an electric charge storagesection, or a photoelectric conversion/storage section 3 having bothconversion and storage functions as in the above example, arow-select-transistor 12, a driving transistor 5 for amplifying anoutput of the photoelectric conversion/storage section 3, and a resettransistor 30 for resetting the electric charge stored in the electriccharge storage section or the photoelectric conversion/storage section3. Further, there are required a number of input/output lines such asthe power supply lines 17 for driving transistors, the row-select-lines11, the pixel-reset-voltage-supply lines 19, the vertical signal lines13 and the like.

This complicates each pixel in arrangement and makes it difficult toenhance the performance thereof. It is also difficult to reduce eachpixel in area to increase the number of pixels in the same area and toreduce the device in size.

In view of the foregoing, it is an object of the present invention toprovide a physical quantity distribution sensor reduced in the number ofinput lines connected to pixels to simplify the pixels in arrangement,thus enabling to increase the number of pixels in the same area and toreduce the device in size.

SUMMARY OF THE INVENTION

The present invention provides a physical quantity distribution sensorcomprising: a plurality of sensor/storage sections each having a sensorelement for sensing a received physical quantity and a storage elementfor storing the information of physical quantity sensed by the sensorelement; a selector for selecting at least one of the plurality ofsensor/storage sections; and a plurality of buffers each capable ofdetecting and supplying the information stored in at least one selectedsensor/storage section, and wherein there is disposed at least oneselection signal transfer line for transferring an output of theselector, that power supply input portions of the buffers are connectedto the selection signal transfer line, and that the buffers are operatedusing, as a power voltage, an output of the selector entered into thebuffers through the selection signal transfer line.

The present invention provides another physical quantity distributionsensor having a plurality of unit cells arranged in N rows and M columns(each of N and M being a natural number not less than 2), each of theplurality of unit cells comprising (i) a sensor/storage section having(a) a sensor element for sensing a physical quantity and (b) a storageelement for storing the information of physical quantity sensed by thesensor element, and (ii) a reset element for resetting the storageelement, and this physical quantity distribution sensor is characterizedin that there are disposed: a row selector for selecting one row out ofthe N rows; buffers in the M columns each for detecting and supplyingthe information stored in the storage element of the sensor/storagesection in a selected row; and N selection signal transfer lines eachfor transferring an output signal of the row selector to each of the Nrows, and that power supply input portions of the buffers in the Mcolumns are connected to the N selection signal transfer lines andarranged to receive a power voltage through the selection signaltransfer line in a selected row.

The present invention provides a further physical quantity distributionsensor comprising: sensor/storage sections each of which is disposed ineach of a plurality of unit cells in a region to be sensed and storedand each of which comprises a sensor element for sensing a receivedphysical quantity and a storage element for storing the information ofsensed physical quantity; a plurality of buffers each of which isassigned to at least one sensor/storage section and each of which isarranged to detect and supply the information stored in the sensorelement of the sensor/storage section; and a selector for selecting atleast one sensor/storage section, and this physical quantitydistribution sensor is characterized in that each of the plurality ofbuffers comprises an electric current control element for controllingthe electric current flowing in each buffer, that an control inputportion of each of the electric current control elements is connected toeach of output portions of the selector, and that only the bufferassigned to the sensor/storage section selected by the selector isoperated.

The present invention provides still another physical quantitydistribution sensor having a plurality of unit cells arranged in N rowsand M columns (N being a natural number not less than 1 and M being anatural number not less than 2), each of the plurality of unit cellscomprising (i) a sensor/storage section having (a) a sensor element forsensing a physical quantity and (b) a storage element for storing theinformation of physical quantity sensed by the sensor element, and (ii)a reset element for resetting the storage element, and this physicalquantity distribution sensor is characterized in that there aredisposed: a column selector for selecting one column out of the Mcolumns; and buffers in the M columns each for detecting and supplyingthe information stored in the storage element of at least onesensor/storage section in a selected column, and that output portions ofthe column selector are respectively connected to input portions ofelectric current control elements of the buffers.

The present invention provides a still further physical quantitydistribution sensor having a plurality of unit cells arranged in N rowsand M columns (N being a natural number not less than 1 and M being anatural number not less than 2), each of the plurality of unit cellscomprising (i) a sensor/storage section having (a) a sensor element forsensing a physical quantity and (b) a storage element for storing theinformation of physical quantity sensed by the sensor element, and (ii)a reset element for resetting the storage element, and this physicalquantity distribution sensor is characterized by comprising: a columnselector for selecting one column out of the M columns; buffers in the Mcolumns each for detecting and supplying the information stored in thestorage element of at least one sensor/storage section in a selectedcolumn; a sensor output portion for externally supplying a signalsupplied from the output portion of each of the buffers; an outputsignal transfer line connected to the sensor output portion directly orthrough an impedance conversion section; and switching elements arrangedsuch that an electric current flows in the buffer in a column selectedby the column selector.

The present invention provides a method of driving a physical quantitydistribution sensor which comprises (i) sensor/storage sections each ofwhich is disposed in each of a plurality of unit cells and each of whichincludes a sensor element for sensing a received physical quantity and astorage element for storing the information of physical quantity sensedby the sensor element, and (ii) buffers each for detecting and supplyingthe information stored in the storage element of at least onesensor/storage section, and in which at least one selection signaltransfer line of a selector for selecting a portion of the plurality ofunit cells, is electrically connected to power supply input portions ofthe buffers, and this driving method is characterized in that selectionof a row to be read out is conducted by supplying a power voltage to thebuffers of the row to be selected.

The present invention provides another method of driving a physicalquantity distribution sensor which comprises (i) sensor/storage sectionseach of which is disposed in each of a plurality of unit cells and eachof which includes a sensor element for sensing a received physicalquantity and a storage element for storing the information of physicalquantity sensed by the sensor element, and (ii) buffers each fordetecting and supplying the information stored in the storage element ofat least one sensor/storage section, and in which at least one selectionsignal transfer line of a first selector for selecting a portion of theplurality of unit cells, is electrically connected to power supply inputportions of the buffers, and this driving method is characterized inthat selection in the nth row to be read out is conducted simultaneouslywith selection of the (n−1)th row to be reset.

The present invention provides a further method of driving a physicalquantity distribution sensor which comprises (i) sensor/storage sectionseach of which is disposed in each of a plurality of unit cells and eachof which includes a sensor element for sensing a received physicalquantity and a storage element for storing the information of physicalquantity sensed by the sensor element, and (ii) buffers each fordetecting and supplying the information stored in the storage element ofat least one sensor/storage section, and in which output portions of asecond selector for column selection are connected to input portions ofelectric current control means of the buffers, and this driving methodis characterized in that column selection and control of an electriccurrent flowing in the buffer in a selected column are conducted at thesame timing.

The present invention provides still another method of driving aphysical quantity distribution sensor which comprises (i) sensor/storagesections each of which is disposed in each of a plurality of unit cellsand each of which includes a sensor element for sensing a receivedphysical quantity and a storage element for storing the information ofphysical quantity sensed by the sensor element, and (ii) buffers eachfor sensing and supplying the information stored in the storage elementof at least one sensor/storage section, and in which a first inputportion of an electric current control means of the buffer in the mthcolumn is connected to a column selector at its output portion for the(m−a)th column (a≧1), and in which a second input portion of theelectric current control means of the buffer in the mth column isconnected to the column selector at its output portion for the (m−b)thcolumn (b≧1), and this driving method is characterized in that anelectric current in the buffer in the mth column rises at the time whenthe (m−a)th column is selected, and falls at the time when the (m−b)thcolumn is selected.

The present invention provides a method of producing a physical quantitydistribution sensor having a plurality of unit cells arranged in N rowsand M columns (each of N and M being a natural number not less than 2),each of the plurality of unit cells comprising (i) a sensor/storagesection having (a) a sensor element for sensing a physical quantity and(b) a storage element for storing the information of physical quantitysensed by the sensor element, and (ii) a reset element for resetting thestorage element, the physical quantity distribution sensor comprising: arow selector for selecting one row out of the N rows; buffers in the Mcolumns each for detecting and supplying the information stored in thestorage element of the sensor/storage section in a selected row; and Nselection signal transfer lines each for transferring an output signalof the row selector to each of the N rows, power supply input portionsof the buffers in the M columns being connected to the N selectionsignal transfer lines and arranged to receive a power voltage throughthe selection signal transfer line in a selected row, each of thebuffers in the M columns having a source follower circuit comprising aplurality of driving elements assigned to the unit cells of each columnand at least one load element connected to the driving elements, andthis producing method is characterized by comprising: a step of formingthe selection signal transfer lines; and a step of forming a wiring forconnecting the driving elements to the load elements, these two stepsforming two wirings different in level from each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating the arrangement of a physical quantitydistribution sensor according to a first embodiment of the presentinvention;

FIG. 2 is a timing chart illustrating a method of driving the physicalquantity distribution sensor in FIG. 1;

FIG. 3 is a view illustrating the arrangement of a physical quantitydistribution sensor according to a second embodiment of the presentinvention;

FIG. 4 is a view illustrating the arrangement of a physical quantitydistribution sensor according to a third embodiment of the presentinvention;

FIG. 5 is a timing chart illustrating a method of driving the physicalquantity distribution sensor in FIG. 4;

FIG. 6 is a view illustrating the arrangement of a physical quantitydistribution sensor according to a fourth embodiment of the presentinvention;

FIG. 7 is a view illustrating the arrangement of a physical quantitydistribution sensor according to a fifth embodiment of the presentinvention;

FIG. 8 is a view illustrating the arrangement of a physical quantitydistribution sensor according to a sixth embodiment of the presentinvention;

FIG. 9 is a view illustrating the arrangement of a physical quantitydistribution sensor according to a seventh embodiment of the presentinvention;

FIG. 10 is a view illustrating the arrangement of a physical quantitydistribution sensor according to an eighth embodiment of the presentinvention;

FIG. 11 is a timing chart illustrating a method of driving the physicalquantity distribution sensor in each of FIGS. 9 and 10; and

FIG. 12 is a view illustrating a physical quantity distribution sensorof prior art.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the accompanying drawings, the following descriptionwill discuss a physical quantity distribution sensor according to thepresent invention and a sensor driving method according to the presentinvention.

(First Embodiment)

FIG. 1 illustrates the arrangement of a physical quantity distributionsensor according to the first embodiment of the present invention. Thissensor is a solid-state imaging device in which unit cells aretwo-dimensionally arranged.

In an imaging area (a region in which physical quantities are to besensed and stored) 31, pixels 32 are arranged in a plurality of rows anda plurality of columns. FIG. 1 shows pixels 32 in the (n−1)th row, thenth row, the (n+1)th row, the (m−1)th column, the mth column and the(m+1)th column (in which each of n and m is a positive integer). Eachpixel 32 has a photoelectric conversion/storage section 33, a drivingtransistor 35 having a gate 34, and a pixel reset transistor 60. Thephotoelectric conversion/storage section 33 serves as a photoelectricconversion element and also as a storage element.

A shift register 36 for row selection successively selects one row outof the plurality of rows through selected-row-drivers 38 each includinga selected-row-driving transistor 40. An electrical potential at theoutput portion 37 assigned to a row to be selected is raised to allowthe driving transistor 40 in the row to be selected. Thus, the shiftregister 36 controls the conductive/nonconductive state of each drivingtransistor 40. A first power supply voltage (Vdd) is applied to eachdriving transistor 40 from a selected-row-driving voltage input portion39. Accordingly, when a selected one of the driving transistors 40 ismade to be electrically conductive, the output of this selected drivingtransistor 40 is substantially equal to the power supply voltage (Vdd).The output of the selected transistor 40 is supplied to the drivingtransistors 35 arranged in the selected row through the associated oneof a plurality of selected-row-power-supply lines 41. In other words,the first embodiment is designed such that the power voltage is suppliedonly to a selected one of the rows with no power voltage supplied to theother rows which are not being selected.

Power input portions of the driving transistors 35 in each row areconnected to the associated one of the plurality ofselected-row-power-supply lines 41. An output portion of each drivingtransistor 35- is connected to a corresponding load transistor 44through the associated one of a plurality of vertical signal lines 43.Each load transistor 44 is connected to a second power supply voltage(Vss) terminal 45 and a gate input portion 46. The electrical potentialat each photoelectric conversion/storage section 33 which varies withthe signal electric charges stored therein determined the electricalpotential at the gate 34 of the associated driving transistor 35. Eachdriving transistor 35 and the corresponding load transistor 44 form asource follower circuit. Each source follower circuit produces anoutput, in accordance with the signal electric charge of the associatedphotoelectric conversion/storage section 33, on the associated verticalsignal line 43.

A shift register 50 for column selection is designed such that, thevoltage of the output portion 51 assigned to a column to be selected israised to allow the associated signal column selection transistor 53 inthe column selection driver 52 to be electrically conductive. As aresult, the electrical potential on the vertical signal line 43 in theselected column, i.e., the output from the source follower circuit inthe selected column, is supplied to a horizontal signal line 54. Thisoutput is then transferred to a device output portion 56 through animpedance conversion section (output buffer) 55.

After the signals are read out from all the pixels in the selected row,the selected-row-reset-driving transistor 59 in the selected row becomeselectrically conductive in response to a reset signal applied from areset voltage input portion 58, thereby to supply a voltage to aselected one of a plurality of pixel-reset-voltage-supply lines 49.According to the voltage on the selected line 49, the pixel resettransistors 60 in the selected row becomes electrically conductive toclear the signal electric charges stored in the photoelectricconversion/storage sections 33 in the selected row. The photoelectricconversion/storage sections 33 again start storing signal electriccharges.

According to the arrangement above-mentioned, an electric power issupplied, through each selected-row-power-supply line 41, to each sourcefollower circuit formed of the driving transistors 35 and thecorresponding load transistor 44. This eliminates interconnection linessuch as the power supply lines 17 (FIG. 12) in the prior art, thussimplifying the sensor in circuit arrangement.

According to the first embodiment, the power supply voltage Vdd appliedto the input portion 39, is used, without being lowered, as the powersource of each source follower circuit. Accordingly, a so-calledembedded transistor is preferably used as each selected-row-drivingtransistor 40. Further, a bootstrap circuit may also be used as eachselected-row-driving transistor 40 with similar effects produced.

With reference to FIGS. 1 and 2, the following description will discussthe operation of the sensor of the first embodiment.

FIG. 2 shows the waveforms of signals in a period 61 during which thenth row is being selected, and in a period 62 during which the (n+l)throw is being selected.

A row selection driving voltage 63 refers to the power supply voltageVdd applied to the selected-row-driving-voltage input portion 39 in FIG.1. The voltage reference point (0 Volt) of the row selection drivingvoltage 63 is generally designated by 64. In the period 61 during whichthe nth row is being selected, a row-select-voltage 65 supplied to theselected-row-power-supply line 41 in the nth row, becomes HIGH. In theperiod 62 during which the (n+1)th row is being selected, arow-select-voltage 66 supplied to the selected-row-power-supply line 41in the (n+1)th row, becomes HIGH.

The following description will discuss in detail how the sensor isdriven when the nth row is being selected.

In the shift register 36 for row selection, the output portion 37assigned to the nth row supplies a row-select-signal to activate theselected-row-driving transistor 40 in the nth row. This electricallyconnects the selected-row-driving-voltage input portion 39 to theselected-row-power-supply line 41 in the nth row. Accordingly, in theperiod 61 during which the nth row is being selected, therow-select-voltage 65 supplied to the selected-row-power-supply line 41in the nth row becomes HIGH. Therefore, the power supply voltage Vdd issupplied to the power supply input portions of the source followercircuits (serving as buffers) each formed of the driving transistor 35in the nth row and the corresponding load transistor 44, such that thepieces of information stored in the photoelectric conversion/storagesections 33 in the nth row are read out. According to the pieces ofinformation thus read, the vertical signal lines 43 each connecting thedriving transistor 35 to the corresponding load transistor 44 arechanged in electrical potential. The changes in electrical potential ofthe vertical signal lines 43 occur for all the columns substantially atthe same time. The load transistor 44 functions as a constant currentsource of the source follower circuit including the load transistor 44and it determines an electric current flowing in that source followercircuit.

In the shift register 50 for column selection, the voltages of theoutput portions 51 are raised, in the form of a pulse, from LOW to HIGHrespectively for the columns to be successively selected. As shown inFIG. 2, a column selection voltage 67 for the (m−1)th column, a columnselection voltage 68 for the mth column and a column selection voltage69 for the (m+1)th column have column selection pulses 72, 73, 74,respectively. Accordingly, the outputs of the source follower circuitsof the corresponding columns are transferred to the output buffer 55.Such transfer is achieved when the signal column selection transistors53 in the respective columns are successively conducted. As a result,the outputs of the source follower circuits assigned to the (m−1)thcolumn, the mth column and the (m+1)th column, respectively, aresupplied as an output voltage 70 through the output buffer 55. Theoutput from the nth-row/(m−1)th-column pixel is generally designated bya reference numeral of 75.

After completion of the output from the pixels arranged in the nth row,a reset voltage 71 applied to the reset voltage input portion 58 israised from LOW to HIGH in the form of a pulse to form a reset pulse 76.This causes all the pixel reset transistors 60 in the nth row to beconducted. The power supply portions of the pixel reset transistors 60in the nth row are connected to the selected-row-power-supply line 41 inthe nth row. Accordingly, when the pixel reset transistors 60 in the nthrow are made to be conductive, the potential levels of the photoelectricconversion/storage sections 33 in the nth row are reset to the level ofthe power supply voltage. Thereafter, the (n+1)th row is selected andsimilar operations are then conducted.

In the first embodiment, the description has been made of thearrangement in which each photoelectric conversion/storage section 33serves as a photoelectric conversion element and also as a storageelement for storing the output of the photoelectric conversion element.However, it is a matter of course that each photoelectricconversion/storage section 33 may comprise a photoelectric conversionelement and a storage element for storing the output of thephotoelectric conversion element. This is also applied to second toeighth embodiments discussed in the following.

(Second Embodiment)

FIG. 3 illustrates the circuit of a physical quantity distributionsensor according to the second embodiment of the present invention. Inthe following, there is omitted a description of those parts in thesecond embodiment which are similar in arrangement to parts in the firstembodiment.

The sensor of the second embodiment differs from the sensor of the firstembodiment in that each pixel further has a selected-row-transistor 42disposed between the driving transistor 35 and the associated verticalsignal line 43. Since the gate input portion of eachselected-row-transistor 42 is connected to the associatedselected-row-power-supply line 41, only the transistors 42 in a selectedrow are made electrically conductive.

According to the second embodiment, it is assured in a wide range ofvoltage that the selected one of the driving transistors 35 in a certainrow is selectively connected to the associated vertical signal line 43.Thus, a wide range of operational voltage can be used.

The timings in a method of driving the sensor of the second embodimentare the same as those in the first embodiment.

(Third Embodiment)

FIG. 4 is a view illustrating the circuit of a physical quantitydistribution sensor according to the third embodiment of the presentinvention. In the following, there is omitted a description of thoseparts in the third embodiment which are similar in arrangement to partsin the first embodiment.

The third embodiment differs from the first embodiment in the followingpoints.

In the third embodiment, the selected-row-reset-driving transistors 59and the pixel-reset-voltage-supply lines 49 in the first embodiment arenot disposed, and the selected-row-power-supply line 79 in the nth row(n=2, 3, . . . N) is connected to input control portions of the pixelreset transistors 80 in the (n−1)th row. In other words, theselected-row-power-supply line 79 in the nth row (n=2, 3, . . . N) alsoserves as a pixel-reset-voltage-supply source for the (n−1)th row.Accordingly, the third embodiment is further simplified in circuitarrangement.

With reference to FIG. 5, the following description will discuss theoperation of the physical quantity distribution sensor of the thirdembodiment.

A row selection driving voltage 63 refers to the power supply voltageVdd applied to the selected-row-driving-voltage input portion 39 in FIG.4. The voltage reference point (0 Volt) of the row selection drivingvoltage 63 is generally designated by 64. In a period 61 during whichthe nth row is being selected, a row selection voltage 65 supplied tothe selected-row-power-supply line 79 in the nth row, becomes HIGH. In aperiod 62 during which the (n+1)th row is being selected, arow-select-voltage 66 supplied to the selected-row-power-supply line 79in the (n+1)th row, becomes HIGH.

In the shift register 36 for row selection, the output portion 37 in thenth row supplies a row-select-signal to activates theselected-row-driving transistor 40 in the nth row. This electricallyconnects the selected-row-driving voltage input portion 39 to theselected-row-power-supply line 79 in the nth row. Accordingly, in theperiod 61 during which the nth row is being selected, therow-select-voltage 65 on the selected-row-power-supply line 79 in thenth row becomes HIGH. Therefore, the power supply voltage Vdd issupplied to the power supply input portions of the source followercircuits. Further, there are conducted (i) the driving transistors 35 inthe selected row and (ii) the selected-row-transistors 42 disposedbetween these driving transistors 35 and the corresponding verticalsignal lines 43. This operates the source follower circuits (buffers)formed of the driving transistors 35 in the nth row and thecorresponding load transistors 44, such that the pieces of informationstored in the photoelectric conversion/storage sections 33 in the nthrow are read out. According to the pieces of information thus read, thevertical signal lines 43 connecting the driving transistors 35 to theload transistors 44 are changed in potential. The changes in potentialof the vertical signal lines 43 occur in all the columns substantiallyat the same time. The load transistor 44 of each column, functions as aconstant electric current source for determining an electric currentflowing in the source follower circuit of the column.

In the shift register 50 for column selection, the voltages of theoutput portions 51 are raised, in the form of a pulse, from LOW to HIGHrespectively for the columns to be successively selected. As shown inFIG. 5, a column selection voltage 67 in the (m−1)th column, a columnselection voltage 68 in the mth column and a column selection voltage 69in the (m+1)th column have column selection pulses 72, 73, 74,respectively. Accordingly, the outputs of the source follower circuits(buffers) of the corresponding columns are transferred to the outputbuffer 55. Such transfer is achieved when the signal column selectiontransistors 53 in the respective columns are successively conducted. Asa result, the outputs of the source follower circuits (buffers) assignedto the (m−1)th column, the mth column and the (m+1)th column,respectively, are supplied as an output voltage 70 through the outputbuffer 55. The output from the nth-row/(m−1)th-column pixel is generallydesignated by a reference numeral of 75.

After completion of the output from all the pixels in the nth row, the(n+1)th row is to be selected. When the (n+1)th row is selected, thepixel reset transistors 80 in the nth row are activated because theselected-row-power-supply line 79 in the (n+1)th row also serves as apixel-reset-voltage-supply source in the nth row. This causes a resetoperation for the nth row to be conducted in the period 62 during whichthe (n+1)th row is being selected.

The row-select-voltage 65 supplied to the selected-row-power-supply line79 in the nth row, has a clock identical with a (n−1)th row reset clock81 supplied to the input portions of the pixel reset transistors 80 inthe (n−1)th row. The row-select-voltage 66 supplied to theselected-row-power-supply line 79 in the (n+1)th row has a clockidentical with an nth row reset clock 82 supplied to the input portionsof the pixel reset transistors 80 in the nth row.

(Fourth Embodiment)

FIG. 6 is a view illustrating the circuit of a physical quantitydistribution sensor according to the fourth embodiment of the presentinvention. In the following, there is omitted a description of thoseparts in the fourth embodiment which are similar in arrangement to partsin the third embodiment.

The fourth embodiment differs from the third embodiment in that thecolumn selection transistor 92 in each column selection driver 91 alsoserves as an electric current switch of the source follower circuit in aselected column.

Each of the first to third embodiments of the present invention and theprior art, is arranged such that, in a period during which a row isbeing selected, an electric current flows in the source followercircuits (buffers) of all the columns. A solid-state imaging device asan example generally has hundreds or thousands of columns. This resultsin enormous power consumption. However, the fourth embodiment isdesigned such that an electric current flows only in the source followercircuit in a selected column. This reduces the power consumption to theorder of about one over hundreds to about one over thousands.Particularly, each of the first to third embodiments is arranged suchthat the electric currents in all the source follower circuits in thesame row are supplied through the selected-row-power-supply line 41, 79.Accordingly, when the current capacity of each power supply line 41, 79is small, there is a possibility of each source follower circuit notoperating normally due to voltage drop. According to the fourthembodiment, an electric current selectively flows only in the sourcefollower circuit in a selected column. Thus, the problem above-mentionedcan be solved.

(Fifth Embodiment)

FIG. 7 is a view illustrating the arrangement of a physical quantitydistribution sensor according to the fifth embodiment of the presentinvention. In the following, there is omitted a description of thoseparts in the fifth embodiment which are similar in arrangement to partsin the fourth embodiment.

The fifth embodiment differs from the fourth embodiment in that theoutput of each source follower circuit is connected to a correspondinghorizontal signal line 93 through a column selection transistor 92.According to the fourth embodiment, all the vertical signal lines 43 arealways connected to one another. It is therefore required that when aselected column is changed, the source follower circuit in the newlyselected column electrically charges all of the vertical signal lines43. Accordingly, the time constant of each source follower circuit isrequired to be small to bring each source follower circuit into a steadystate as early as possible. To this end, the driving transistor 35 ineach pixel 32 must be increased in size. In view of the miniaturizationof the sensor, however, restrictions are imposed to the sizes of eachdriving transistor 35.

According to the fifth embodiment, the output portion of the sourcefollower circuit in a selected column is not connected to the verticalsignal lines 43 in other columns. Thus, the capacitance to beelectrically charged by one source follower circuit is reduced to theorder of one over hundreds to one over thousands as compared with thefourth embodiment. This hardly causes trouble of lengthening theelectrically charging time. According to the fifth embodiment, the loadtransistors 44 respectively assigned to the columns may be replaced witha single common load transistor.

(Sixth Embodiment)

FIG. 8 illustrates the circuit arrangement of a physical quantitydistribution sensor according to the sixth embodiment of the presentinvention. In the following, there is omitted a description of thoseparts in the sixth embodiment which are similar in arrangement to partsin the fourth embodiment.

The sixth embodiment differs from each of the fourth and fifthembodiments in the following points (a), (b) and (c).

(a) In each pixel, an electric current control column selectiontransistor 95 is disposed independently from the column selectiontransistor 92.

(b) The gate of each electric current control column selectiontransistor 95 is connected to the corresponding output portion 51 of theshift register 50 for column selection.

(c) Each vertical signal line 43 is connected to the horizontal signalline 93 through the associated column selection transistor 92.

With the arrangement above-mentioned, an electric current flows only inthe source follower circuit in a selected column. Further, only thevertical signal line 43 for a selected column is connected to thehorizontal signal line 93, and only the load transistor 44 in theselected column functions as the load transistor of the source followercircuit.

(Seventh Embodiment)

FIG. 9 illustrates the circuit arrangement of a physical quantitydistribution sensor according to the seventh embodiment of the presentinvention. In the following, there is omitted a description of thoseparts in the seventh embodiment which are similar in arrangement toparts in the sixth embodiment.

According to each of the fourth to sixth embodiments, each columnselection period for signal reading is equal to each column selectionperiod for letting flow an electric current in each source followercircuit. This causes no inconvenience when a time constant during whichthe output of each source follower circuit is brought into a steadystate from the time an electric current starts flowing therein, issufficiently small as compared with a period during which a signal in aselected column is supplied. However, there are instances where theelectric current driving ability of each driving transistor 35 cannotsufficiently be increased in view of size or the like, or wherecapacitance of each vertical signal line 43 is not large due to a largenumber of pixels arranged in the vertical direction. In such instances,each period during which an electric current flows in each sourcefollower circuit, is required to be longer than each signal outputperiod.

The seventh embodiment is designed such that a time period during whichan electric current flows in a certain source follower circuit can bedetermined independently from the signal output period. Morespecifically, a voltage generating circuit section 97 is disposed ineach column. Each voltage generating circuit section 97 comprises afirst input portion 98, a second input portion 99 and an output portion100, and is arranged to supply a predetermined potential to the outputportion 100 in a period between the time when the first input portion 98receives a predetermined signal and the time when the second inputportion 99 receives a predetermined signal.

The following description will discuss the voltage generating circuitsection 97 for the source follower circuit in the mth column. The firstinput portion 98 of the voltage generating circuit section 97 isconnected to an output portion for the (m−1)th column 51-a of the shiftregister for column selection 50. The second input portion 99 of thevoltage generating circuit section 97 is connected to an output portionfor the (m+1)th column 51-b of the shift register for column selection50. The voltage output portion 100 in the mth column is connected to thegate of the electric current control column selection transistor 95 inthe mth column.

When the (m−1)th column is selected by the shift register 50, thevoltage generating circuit section 97 in the mth column receives anoutput from the output portion for the (m−1)th column 51-a of the shiftregister 50 through the first input portion 98. Then, the voltagegenerating circuit section 97 increases the potential of the outputportion 100 in the mth column from LOW to HIGH, and maintains thepotential thus increased. Accordingly, before the mth column a isactually selected, an electric current starts flowing in the sourcefollower circuit in the mth column, thus starting a data readingoperation. Thereafter, when the (m+1)th column is selected by the shiftregister for column selection 50, the voltage generating circuit section97 in the mth column receives, through the second input portion 99, anoutput from the output portion for the (m+1)th column 51-b of the shiftregister for column selection 50, and then stops operating. Morespecifically, the output portion 100 in the mth column is lowered inpotential from HIGH to LOW to finish the reading operation using thesource follower circuit in the mth column.

(Eighth Embodiment)

FIG. 10 is a view illustrating the arrangement of a main portion of aphysical quantity distribution sensor according to the eighth embodimentof the present invention. Basically, the eighth embodiment has anarrangement similar to that of the seventh embodiment, but is differenttherefrom in the voltage generating circuit section. In the following,there is omitted a description of those parts in the eighth embodimentwhich are similar in arrangement to parts in the seventh embodiment.

A voltage generating circuit section 101 in FIG. 10 corresponds to anelectric current control selection voltage generating circuit section 97in FIG. 9, and is a circuit having a known arrangement which is called astatic RS flip-flop circuit or a bistable unit.

The circuit section 101 has a first power supply input portion (Vdd)102, a second power supply input portion (Vss) 103, a first inputportion 104, a second input portion 105 and an output portion 106.Inside of the circuit section 101, six transistors are mutuallyconnected as shown in FIG. 10. The first input portion 104, the secondinput portion 105 and the output portion 106 respectively correspond tothe first input portion 98, the second input portion 99 and the electriccurrent control selection voltage output portion 100 of each electriccurrent control selection voltage generating circuit section 97 in FIG.9.

This circuit section 101 is a so-called bistable circuit and is operatedsuch that the output portion 106 is brought into a first power voltagestate by a positive pulse given to the first input portion 104 and thatthe output portion 106 is brought into a second power voltage state by apositive pulse given to the second input portion 105.

With reference to FIG. 11, the following description will discuss amethod of driving the sensor according to the eighth embodiment.

In FIG. 11, column selection voltages 110, 111, 112 for the (m−1)thcolumn, the mth column, the (m+1)th column are voltages of the outputportions 51 of the shift register for column selection 50. Columnselection pulses 113, 114, 115 respectively show the selection states ofthe (m−1)th column, the mth column, the (m+1)th column. Electric currentcontrol column selection voltages 116, 117, 118 for the (m−1)th column,the mth column, the (m+1)th column, are voltages of the output portions106 of the electric current control selection voltage generating circuitsections 101 for the (m−1)th column, the mth column, the (m+1)th column.Electric current control column selection pulses 119, 120, 121respectively show the electric current control selection states of the(m−1)th column, the mth column, the (m+1)th column.

In the following description, the electric current control columnselection pulse 120 for the mth column is taken as an example. The pulse120 is brought into the first power supply voltage state at the risingof the (m−1)th column selection pulse 113, and is brought into thesecond power voltage state at the rising of the (m+1)th column selectionpulse 115. More specifically, an electric current starts flowing in thesource follower circuit in the mth column before the mth column isselected as a column to be supplied, and the flow of an electric currentin the source follower circuit in the mth column is stopped after theoutput in the mth column has been finished.

According to the eighth embodiment, the wirings are installed such thatthe pulse 120 for the mth column rises at the rising of the (m−1)thcolumn selection pulse 113, and falls at the rising of the (m+1)thcolumn selection pulse 115. However, it is a matter of course thatprovision may be made such that the pulse 120 rises at the rising of afurther preceding column selection pulse. With such an arrangement, anelectric current can flow in the source follower circuit earlier. As tothe falling of the pulse 120, too, it is possible to set, as necessary,such that the pulse 120 falls later than the rising of the pulse 115.

A so-called bistable unit is shown in FIG. 10, as a specific example ofthe voltage generating circuit section for the electric current controlsection. However, the circuit section is not limited to such a circuitarrangement, but a CMOS circuit of such a bistable unit or other logiccircuit may also be used. As an example, there is shown a circuit ofwhich output rises or falls at the rising of a clock applied to an inputportion thereof. However, there may also be used a circuit of whichoutput rises or falls at the falling of a clock applied to an inputportion thereof.

In the foregoing, the description has been made of each of the fourth toeighth embodiments having the arrangement of pixels and row selectionportions identical with that of the third embodiment. However, each ofthe fourth to eighth embodiments may have an arrangement of pixels androw selection portions identical with that of each of the first to thirdembodiments, or identical with that of prior art.

In the arrangement of prior art in FIG. 12, it is only the verticalsignal lines 13 and the power supply lines 17 that are required to be oflow resistance (large electric current capacity). In the pixels 2severely limited in view of designing, these lines 13, 17 can bedisposed in parallel to each other and can be formed in the same wiringlayer (for example, metallic layer) of low resistance. In each of theembodiments of the present invention shown in FIGS. 1 to 11, however, itis the selected-row-power-supply lines 41 and the vertical signal lines43 that are required to be of low resistance (large electric currentcapacitance). As shown in FIG. 1, these liens 41, 43 are not parallel toeach other, but are at right angles to each other. To achieve eachembodiment of the present invention, it is much easier to form theselines 41, 43 by wiring layers different in level from each other, thanto form these lines 41, 43 by the same wiring layer.

In each of the embodiments above-mentioned, the description has beenmade, for simplification, of the arrangement having photoelectricconversion/storage sections serving as photoelectric conversion elementsand also as signal electric charge storage elements. However, it is amatter of course that the present invention may be arranged such thatphotoelectric conversion elements and signal electric charge storageelements are independently disposed.

In the foregoing, the description has been made of the arrangement inwhich each output is supplied through the output buffer. However, it isapparent that the output buffer is not an indispensable element of thepresent invention.

Further, the foregoing description has been made with a solid-stateimaging device taken as an example. However, when the sensor is equippedwith sensor elements for sensing the physical quantity of x-rays,infrared rays, temperature, a magnetic field, an electric field,pressure or the like, and when provision is made such that the potentialof each sensor elements changed due to received physical quantity, istransferred to the gate of each driving transistor, it is a matter ofcourse that the present invention is also effective for a generalphysical quantity distribution sensor for other substance than light.

Further, the foregoing description has been made of the arrangement inwhich the unit cells are two-dimensionally arranged. However, thepresent invention is effective for the arrangement in which the unitcells are one-dimensionally arranged.

In each of the embodiments above-mentioned, a shift register is used foreach of row and column selectors. However, a decoder may be used,instead of such a shift register, with similar effects produced.

According to the present invention, the lines each interconnecting a rowof pixels have a row selection function, a power voltage supply functionand a reset function, thus achieving a physical quantity distributionsensor simple in arrangement.

What is claimed is:
 1. A physical quantity distribution sensor having aplurality of unit cells arranged in N rows and M columns (each of N andM being a natural number not less than 2), each of said plurality ofunit cells comprising (i) a sensor/storage section for sensing andstoring information of a physical quantity, and (ii) a reset element forresetting said sensor/storage section, wherein said sensor comprises: arow selector for selecting one row out of said N rows; buffers in said Mcolumns each for detecting and supplying information stored in thesensor/storage section in a selected row; and N selection signaltransfer lines each for transferring an output signal of said rowselector to each of said N rows, power supply input portions of saidbuffers in said M columns being connected to said N selection signaltransfer lines, and arranged to receive a power voltage through theselection signal transfer line in a selected row, and the selectionsignal transfer line in the nth row (n=2, 3, . . . N) being connected toinput portions of the reset elements in the (n−1)th row.
 2. The physicalquantity distribution sensor of claim 1, wherein each of said buffers insaid M columns has a source follower circuit comprising (i) a driveelement and (ii) at least one load element connected to said driveelement.
 3. The physical quantity distribution sensor of claim 2,wherein each of said plurality of unit cells further comprises aswitching element for controlling the electric connection/disconnectionbetween the-drive element and load element, control input portions ofthe switching elements in each row being connected to the selectionsignal transfer line in each row.
 4. A physical quantity distributionsensor having a plurality of unit cells arranged in N rows and M columns(N being a natural number not less than 1 and M being a natural numbernot less than 2), each of said plurality of unit cells comprising asensor/storage section for sensing and storing information of a physicalquantity, wherein said sensor comprises: a column selector for selectingone column out of said M columns; and buffers in said M columns each fordetecting and supplying the information stored in the sensor/storagesection in a selected column, each of said buffers in said M columnscomprising an electric current control circuit having a first inputportion and a second input portion for operating each of said buffersbetween the time when said first input portion receives a predeterminedsignal and the time when said second input portion receives apredetermined signal, and the first input portion of the electriccurrent control circuit of the buffer in the mth column being connectedto said column selector at its output portion for the (m−a)th column(a≧1), and the second input portion of said electric current controlcircuit of said buffer in the mth column being connected to said columnselector at its output portion for the (m+b)th column (b≧1).
 5. Thephysical quantity distribution sensor of claim 4, wherein each of saidelectric current control circuits is formed of a bistable circuit.
 6. Amethod of driving a physical quantity distribution sensor whichcomprises (i) sensor/storage sections each of which is disposed in eachof a plurality of unit cells and each of which is for sensing andstoring information of a physical quantity, and (ii) buffers each fordetecting and supplying the information stored in the sensor/storagesection in a selected row, and in which at least one selection signaltransfer line of a row selector for selecting a portion of saidplurality of unit cells, is electrically connected to power supply inputportions of said buffers, wherein the selection signal transfer line inthe nth row to be read out being connected to input portion of resetelements in the (n−1) row.
 7. A method of driving a physical quantitydistribution sensor which comprises (i) sensor/storage sections each ofwhich is disposed in each of a plurality of unit cells and each of whichis for sensing and storing information of a physical quantity, and (ii)buffers each for detecting and supplying the information stored in thesensor/storage section in a selected row, and in which a first inputportion of an electric current control means of the buffer in the mthcolumn is connected to a column selector at its output portion for the(m−a)th column (a≧1), and in which a second input portion of saidelectric current control means of said buffer in said mth column isconnected to said column selector at its output portion for the (m+b)thcolumn (b≧1), wherein an electric current in said buffer in said mthcolumn rises at the time when the (m−a)th column is selected, and fallsat the time when the (m+b)th column is selected.